Basically, I can observe plaques in the dilution of 10^2- 10^5. However, when I remove the agarose layer, the cells come of with the overlay. Therefore, I cannot fix and stain the cells. Should I fix the cells first then remove the overlay or anyone can suggest me a better idea? Currently my lab is using 7.4%Formaldehyde/PBS for fixing and 0.1% crystal violet for staining.

I will be glad if anyone can help. Thanks

-vinnie_133-

You aren't supposed to remove the agarose before fixing and staining. Add your fixative straight on top of the agarose and then incubate at room temperature (overnight should do it). Then you wash the agarose off before reading your plaque assays.